Conventional paging receivers utilize many types of antennas for receiving signals having specific frequencies. Typically, antenna size and shape varies with both the frequency of the signals the antenna is to receive and the size and shape of the paging receiver which houses the antenna. For instance, in many low frequency applications, such as in the low VHF (very high frequency) bands, the antenna takes the form of a ferrite loop antenna connected to the receiver. In the UHF (ultra high frequency) band, antennas are often wireform loop antennas or dipole antennas. In each case, however, the antenna must not only function electrically, but also physically fit into the paging receiver.
As technology has advanced, a greater number of features has been included in paging receivers due to customer demands. Many of these features, such as alphanumeric displays, real time clocks and alarms, musical alerts, etc., require a large amount of complex circuitry for implementation, which tends to increase the size of a paging receiver including such features. At the same time, however, market trends have dictated that paging receivers become smaller and lighter such that a user can easily carry a paging receiver without strain or discomfort. These conflicting requirements have necessarily resulted in paging receivers in which the space available for accommodating an antenna has decreased. One solution to this problem is to reduce the size of the antenna. This cannot always be done, however, without adversely affecting the electrical performance of the radio receiver.
In addition to becoming smaller, paging receivers have, in response to customer demand, been manufactured in various form factors for customer convenience. For example, paging receivers have been manufactured in a "credit card" or pen form for carrying in a shirt pocket and a watch form for wearing on the wrist. The number of different form factors in which paging receivers are manufactured is almost limitless, and, for each of these different form factors, antennas must be designed which not only physically fit within the paging receiver, but also function electrically such that the paging receiver can receive the desired signals.
Additionally, antennas which are internal are usually surrounded by components which are not part of the antenna but which can interact with the antenna to reduce its gain and performance. Thus, what is needed is an antenna which can be better isolated from its environment, allowing for compact and internal antenna designs which meet or exceed the performance of conventional antenna designs.